In response to the demands of consumers who are driven both by ever-escalating fuel prices and the dire consequences of global warming, the automobile industry is slowly starting to embrace the need for ultra-low emission, high efficiency cars. While some within the industry are attempting to achieve these goals by engineering more efficient internal combustion engines, others are incorporating hybrid or all-electric drive trains into their vehicle line-ups. To meet consumer expectations, however, the automobile industry must not only achieve a greener drive train, but must do so while maintaining reasonable levels of performance, range, reliability, safety and cost.
Electric vehicles, due to their reliance on rechargeable batteries, require a relatively sophisticated thermal management system to insure that the batteries remain within their desired operating temperature range while still providing adequate heating and cooling within the passenger cabin and not unduly affecting the vehicle's overall operating efficiency. A variety of approaches have been taken to try and meet these goals. For example, U.S. Pat. No. 6,360,835 discloses a thermal management system for use with a fuel-cell-powered vehicle, the system utilizing both low and high temperature heat transfer circuits that share a common heat transfer medium, the dual circuits required to adequately cool the vehicle's exothermic components and heat the vehicle's endothermic components.
U.S. Pat. No. 7,789,176 discloses a thermal management system that utilizes multiple cooling loops and a single heat exchanger. In an exemplary embodiment, one cooling loop is used to cool the energy storage system, a second cooling loop corresponds to the HVAC subsystem, and a third cooling loop corresponds to the drive motor cooling system. The use of a heater coupled to the first cooling loop is also disclosed, the heater providing a means for insuring that the batteries are warm enough during initial vehicle operation or when exposed to very low ambient temperatures.
U.S. Pat. No. 8,336,319 discloses an EV dual mode thermal management system designed to optimize efficiency between two coolant loops, the first cooling loop in thermal communication with the vehicle's batteries and the second cooling loop in thermal communication with at least one drive train component such as an electric motor or an inverter. The disclosed system uses a dual mode valve system to configure the thermal management system between a first mode and a second mode of operation, where in the first mode the two cooling loops operate in parallel and in the second mode the two cooling loops operate in series.
Although the prior art discloses numerous techniques for cooling the battery pack of an electric vehicle, an improved thermal management system is needed that is capable of maintaining the batteries within their desired operating temperature range while still providing means for optimizing overall vehicle operating efficiency. The present invention provides such a thermal management system.